1. Field of the Invention
The present invention relates to a polyester of polyhydroxyalkanoate (PHA) type that comprises a novel unit and to a production method thereof utilizing a microorganism. More specifically, it relates to a PHA polyester that comprises a 3-hydroxy-xcfx89-(4-vinylphenyl)alkanoic acid unit and to a production method of such a PHA utilizing a microorganism that can produce the PHA using xcfx89-(4-vinylphenyl)alkanoic acid as a raw material.
2. Related Background Art
So far, it is known that a large number of microorganisms produce poly-3-hydroxybutyrate (PHB) or other PHAs and accumulate them within the cell (xe2x80x9cBiodegradable Plastics Handbookxe2x80x9d, edited by Biodegradable Plastics Society, published by N.T.S. Co., Ltd., p.178-197 (1995)). These microbial polymers such as PHA can be used for producing various products by the melting process just as conventional plastics. Further, microbial polymers such as PHA have biodegradability which provides an advantage that they are completely decomposed by microorganisms in nature. Thus, for example, unlike conventional synthetic polymer compounds, discarded microbial PHA would not remain as it is in the natural environment or would not cause pollution. Further, microbial PHA generally has good biocompatibility and its application to a medical soft member is expected.
It is also known that the composition and constitution of microbial PHA varies depending to the microorganism used for production, culture medium composition, culturing conditions and the like. So far, mainly in order to improve physical properties of PHA, studies to control the composition and structure of microbial PHA have been conducted.
As part of studies to control the composition and structure of microbial PHA, recently various studies have been carried out in order to make microorganisms produce PHA having an aromatic ring on the unit.
There are reports that Pseudomonas oleovorans produces PHA comprised of 3-hydroxy-5-phenylvaleric acid units using 5-phenylvaleric acid as a substrate (Makromol. Chem., 191, 1957-1965 (1990) and Macromolecules, 24, 5256-5260 (1991)).
In Macromolecules, 29, 1762-1766 (1996), it is reported that using 5-(p-tolyl)valeric acid as a substrate, Pseudomonas oleovorans produces PHA comprised of 3-hydroxy-5-(p-tolyl)valeric acid units.
In Macromolecules, 32, 2889-2895 (1999), it is reported that using 5-(2,4-dinitrophenyl)valeric acid as a substrate, Pseudomonas oleovorans produces PHA containing 3-hydroxy-5-(2,4-dinitrophenyl)valeric acid units and 3-hydroxy-5-(p-nitrophenyl)valeric acid units.
In Macromol. Chem. Phys., 195, 1665-1672 (1994), it is reported that using 11-phenoxyundecanoic acid as a substrate, Pseudomonas oleovorans produces PHA copolymer containing 3-hydroxy-5-phenoxyvaleric acid units and 3-hydroxy-9-phenoxynonanoic acid units.
Japanese Patent Publication No. 2989175 discloses a homopolymer comprised of 3-hydroxy-5-(monofluoro phenoxy)pentanoate (3H5 (MFP)P) units or 3-hydroxy-5-(difluoro phenoxy)pentanoate (3H5 (DFP) P) units; a copolymer containing at least 3H5 (MFP)P units or 3H5 (DFP)P units; Pseudomonas putida having an ability to produce these polymers; and a production method thereof using Pseudomonas species. It also discloses that the microorganism can produce polymers having phenoxy groups substituted with one or two fluorine atoms at the end of the side chains by assimilating long chain fatty acids having such a substituted phenoxy group, and as the advantage of the invention, it is written that such a polymer has a high melting point and good workability, further providing stereoregularity and water repellency.
Also, other than the fluorine substituted PHA having fluorine atoms on the aromatic ring in the unit, PHAs having cyano and/or nitro substituents on the aromatic ring in the unit have been studied.
Can. J. Microbiol., 41, 32-43 (1995) and Polymer International, 39, 205-213 (1996) report that PHA containing 3-hydroxy-6-(p-cyanophenoxy)hexanoic acid or 3-hydroxy-6-(p-nitrophenoxy)hexanoic acid as a monomer unit is yielded by Pseudomonas oleovorans ATCC 29347 or Pseudomonas putida KT 2442 using octanoic acid and 6-(p-cyanophenoxy)hexanoic acid or 6-(p-nitrophenoxy)hexanoic acid as the substrates.
PHA containing such a unit having a substituted aromatic ring is a multifunctional PHA because it has functions due to the substituents of the aromatic rings and properties such as a high melting point and good workability due to the aromatic rings.
On the other hand, studies have been vigorously carried out to obtain multifunctional PHA by introducing desired functional groups to the side chains of PHA polymer having a vinyl group in the unit through chemical conversion utilizing the vinyl groups.
Polymer, 41, 1703-1709 (2000) reports that a polyester having a vinyl group on the side chains was yielded by a Pseudomonas and then the vinyl groups were oxidized to produce a polyester having a hydroxyl group on the side chains.
Macromolecules, 31, 1480-1486 (1998) reports that polyester having vinyl groups on the side chains was yielded by Pseudomonas oleovorans and then the vinyl groups were epoxidized to produce a polyester having an epoxy group on the side chains.
Polymer, 40, 3787-3793 (1999) reports analysis of the crosslinking reaction and products when a polymer that has an epoxy group on the side chains and was produced by a similar method was heated with hexamethylenediamine.
Further, Polymer, 35, 2090-2097 (1994) reports that physical properties of polyester were improved by crosslinking reaction within the polyester molecule using vinyl groups on the side chains of the polyester.
As seen from above studies, vinyl group, being an unsaturated hydrocarbon group, is highly reactive in addition reaction etc., so that vinyl group can be used to introduce various functional groups and to carry out chemical conversion. Further, a vinyl group can be a foothold or a crosslinking point in the polymer crosslinking reaction. Consequently, in view of PHA application as a functional material, it is very useful to have a vinyl group in the unit that constitutes PHA.
All of known polyester polymers having vinyl groups have a structure where vinyl groups are born at the end of alkyl side chains directly bonded to the skeletal structure of the polyester. However, polyesters having alkyl side chains generally do not have so high glass transition temperature and melting point and its thermal characteristics are not always favorable in melt-processing, and there are not many materials having excellent properties as film or processed goods. On the other hand, polyester having an aromatic ring in the side chain, as already described, has generally a high melting point and good workability.
Accordingly, it is desirable to use polyester having aromatic rings and vinyl groups together on the side chains to develop new functional polymers having excellent processing properties. So far, there is no report indicating that an aromatic ring and a functional group such as the vinyl group were introduced in a side chain of polyester.
The present invention is to solve the above described problem, and an object of the present invention is to provide polyester having an aromatic ring and a vinyl group on the side chain, especially PHA polyester having biodegradability and its production method. More specifically, the present invention provides a PHA polyester having an aromatic ring having a vinyl substituent on the ring on a side chain and a production method thereof using a microorganism.
The present inventors concentrated on the study to achieve the above-described object, and accomplished the present invention described in the following.
According to an aspect of the present invention there is provided a polyhydroxyalkanoate type polyester comprising one unit % or more of 3-hydroxy-xcfx89-(4-vinylphenyl)alkanoic acid unit represented by chemical formula (1): 
where n is one or more integers arbitrarily selected from 0 to 7.
Polyester in the present invention, if circumstances require, may contain 3-hydroxy alkanoic acid units shown by the following chemical formula (2) in addition to the above 3-hydroxy-xcfx89-(4-vinylphenyl)alkanoic acid unit. 
(m is one or more integers arbitrarily selected from the range shown in the formula.)
An example of such a polyester includes polyester containing one unit % of more of 3-hydroxy-5-(4-vinylphenyl)valeric acid units shown by the following chemical formula (3) in the molecule. 
According to another aspect of the present invention, there is provided a method of producing the above-described PHA polyester comprising the steps of:
(1) providing xcfx89-(4-vinylphenyl)alkanoic acid represented by chemical formula (4) as a raw material, 
where p is one or more integers arbitrarily selected from 0 to 7; and
(2) producing a polyester comprising one unit % or more of 3-hydroxy-xcfx89-(4-vinylphenyl)alkanoic acid unit represented by chemical formula (1) by using a microorganism capable of producing the polyester from the xcfx89-(4-vinylphenyl)alkanoic acid; 
where n is one or more integers arbitrarily selected from 0 to 7.